Estoy tratando de crear un jar ejecutable para mi aplicación JavaFX dentro de un proyecto Eclipse Maven.

Estoy siguiendo este hilo:Aplicación JavaFx con Maven en Eclipse

Y este turotial:https://www.youtube.com/watch?v=wbjW8rYlook

Estoy obteniendo un
No plugin found for prefix 'jfx' in the current project and in the plugin groups
error al intentar ejecutar el objetivo:jfx:jar

Error de compilación completa:

[INFO] Scanning for projects...
[INFO] Downloading: https://repo.maven.apache.org/maven2/com/zenjava/javafx-maven-plugin/8.1.2/javafx-maven-plugin-8.1.2.pom
[WARNING] Failed to retrieve plugin descriptor for com.zenjava:javafx-maven-plugin:8.1.2: Plugin com.zenjava:javafx-maven-plugin:8.1.2 or one of its dependencies could not be resolved: Failed to read artifact descriptor for com.zenjava:javafx-maven-plugin:jar:8.1.2
[INFO] Downloading: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-release-plugin/2.3.2/maven-release-plugin-2.3.2.pom
[WARNING] Failed to retrieve plugin descriptor for org.apache.maven.plugins:maven-release-plugin:2.3.2: Plugin org.apache.maven.plugins:maven-release-plugin:2.3.2 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-release-plugin:jar:2.3.2
[INFO] Downloading: https://repo.maven.apache.org/maven2/com/zenjava/maven-metadata.xml
[INFO] Downloading: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-metadata.xml
[INFO] Downloading: https://repo.maven.apache.org/maven2/org/codehaus/mojo/maven-metadata.xml
[WARNING] Could not transfer metadata com.zenjava/maven-metadata.xml from/to central (https://repo.maven.apache.org/maven2): sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
[WARNING] Could not transfer metadata org.apache.maven.plugins/maven-metadata.xml from/to central (https://repo.maven.apache.org/maven2): sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
[WARNING] Could not transfer metadata org.codehaus.mojo/maven-metadata.xml from/to central (https://repo.maven.apache.org/maven2): sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
[WARNING] Failure to transfer com.zenjava/maven-metadata.xml from https://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer metadata com.zenjava/maven-metadata.xml from/to central (https://repo.maven.apache.org/maven2): sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
[WARNING] Failure to transfer org.apache.maven.plugins/maven-metadata.xml from https://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer metadata org.apache.maven.plugins/maven-metadata.xml from/to central (https://repo.maven.apache.org/maven2): sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
[WARNING] Failure to transfer org.codehaus.mojo/maven-metadata.xml from https://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer metadata org.codehaus.mojo/maven-metadata.xml from/to central (https://repo.maven.apache.org/maven2): sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.831 s
[INFO] Finished at: 2017-01-18T15:36:52+08:00
[INFO] Final Memory: 9M/22M
[INFO] ------------------------------------------------------------------------
[ERROR] No plugin found for prefix 'jfx' in the current project and in the plugin groups [com.zenjava, org.apache.maven.plugins, org.codehaus.mojo] available from the repositories [local (C:\Users\alexismatunog\Documents\My Docs\03_OE\Java\workspace\Maven\m2\repository), central (https://repo.maven.apache.org/maven2)] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/NoPluginFoundForPrefixException

Ya he intentado lo siguiente en un intento de resolver este problema:
1. Ingresemvn clean install (CONSTRUIR ÉXITO)
2. Agregado<pluginGroup>com.zenjava</pluginGroup> en settings.xml

Además, ya he agregado el<plugin> nodo en mi pom.xml

    <plugin>
        <groupId>com.zenjava</groupId>
        <artifactId>javafx-maven-plugin</artifactId>
        <version>8.1.2</version>
        <configuration>
            <mainClass>com.sample.MainApp</mainClass>
        </configuration>
    </plugin>

¿Como puedó resolver esté problema?

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ACTUALIZACIÓN 1:
Después de seguir la respuesta de Jaydeep, recibo un mensaje de contraseña después de intentar abrir el archivo cacerts y no puedo continuar.

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ACTUALIZACIÓN 2:
La contraseña predeterminada para cacerts es "changeit".La construcción es exitosa después de importar el certificado raíz. Además, he actualizado mi archivo pom con el complemento jfx versión 8.7.0 según lo recomendado por FibreFoX.